Image descriptionLight-microscope image of the specimen shown in Fig. 000005a following intensification with OsO4. The image is much clearer due to the enhanced contrast between the DAB-positive and -negative areas.

Characteristic findings

Following immunostaining and DAB color development, paraffin sections of pathologic tissue samples were subjected to OsO4 intensification. As a result of this treatment, the brown color of DAB-positive areas became much darker, making the areas clearly distinct from the neighboring tissue under a light microscope. As suggested by this result, OsO4 staining also highly enhances the contrast between DAB-positive and -negative areas in LVSEM images. Thus, when OsO4-intensified tissue sections are observed at higher magnifications, the morphology of subcellular compartments, such as the nucleus, can be studied in detail. 11)

Observations

Fig. 000005a shows a light-microscope image of a specimen that was immunostained for SOD1 and developed with DAB. It is a paraffin section of pathologic tissue obtained from a patient with breast cancer (invasive ductal carcinoma). The same specimen was then treated with 2% OsO4 for 1 hour to intensify DAB staining. The result is shown in Image Fig. 000005b. The comparison of these two light-microscope images clearly indicates that OsO4 treatment enhances the contrast of DAB-positive, brown ductal epithelial cells.